For example, Patent Documents 1 and 2 below describe a power control device that supplies, to a load such as a heater, power proportional to a manipulated signal (target value) output from a PID controller.
This power control device switches on and off the power supplied to the load at time intervals corresponding to an integral multiple a half cycle of a power source waveform (hereinafter referred to as “unit time”), and supplies to the load the power proportional to the manipulated signal (target value) output from the PID controller by controlling a time rate of ON time during which the power is supplied to OFF time during which the power is not supplied.
Below, a mode for controlling the power with this power control device is referred to as “time-divisional output control mode”.
In control of the power supplied to N loads (channels), when each channel is controlled in the time-divisional output control mode, the number of channels powered at one time (the number of channels turned on at one time) in each unit time ranges between 0 (all channels are OFF) and N (all channels are ON).
FIG. 6 is a diagram showing one example of ON/OFF states of channels when power control is conducted for 16 channels in the time-divisional output control mode.
As evidenced by FIG. 6, all of the 16 channels may be OFF, or all of the 16 channels may be ON. Therefore, the number of channels turned on at one time ranges between 0 and 16.
Further, Patent Documents 3-5 below disclose a power control method for suppressing a total output power value (sum of consumed power values in one or more channels being powered) to or below a preset power upper limit value (upper limit value of supplied power values with respect to all of the channels per unit time) in each unit time by limiting the number of channels powered at one time in each unit time (hereinafter referred to as “peak power suppression control”).